use std::{
    collections::{HashMap, HashSet},
    net::SocketAddr,
    sync::Arc,
};

use anyhow::{bail, Context, Result};
use axum::{
    body::Body,
    extract::{
        ws::{Message, WebSocket},
        Path, Request, State, WebSocketUpgrade,
    },
    http::StatusCode,
    middleware::{self, Next},
    response::{IntoResponse, Response},
    routing::{get, post},
    Extension, Form, Router,
};
use axum_extra::extract::CookieJar;
use maud::{html, Markup, PreEscaped, DOCTYPE};
use rand::random;
use serde::Deserialize;
use tokio::sync::{
    broadcast::{self, Receiver, Sender},
    Mutex,
};
use tower_http::{
    catch_panic::CatchPanicLayer,
    services::ServeDir,
    trace::{DefaultMakeSpan, DefaultOnResponse, TraceLayer},
};
use tracing::{error, info, trace, warn, Level};
use tracing_subscriber::FmtSubscriber;

/// If a handler panics we run this function and return the [Response].
fn handle_panic(err: Box<dyn std::any::Any + Send + 'static>) -> Response {
    let details = if let Some(s) = err.downcast_ref::<String>() {
        s.clone()
    } else if let Some(s) = err.downcast_ref::<&str>() {
        s.to_string()
    } else {
        "Unknown panic message".to_string()
    };
    error!(details = details, "Handler paniced");

    (StatusCode::INTERNAL_SERVER_ERROR).into_response()
}

#[derive(Deserialize, Debug, Clone)]
struct NoteDatum {
    // Epoch time in ms
    time: u64,
    // Fraction up/down
    y: f64,
}

#[derive(Deserialize, Debug, Clone)]
struct Notes {
    notes: Vec<NoteDatum>,
}

#[derive(Deserialize)]
struct NotesForm {
    notes: String,
}

struct Round {
    author: UserId,
    notes: Notes,
    guesses: HashMap<UserId, String>,
}

struct Game {
    id: u64,

    // If we've started or not
    is_started: bool,

    /// All users that are in the game.
    active_users: HashSet<UserId>,
    /// All submissions
    submissions: HashMap<UserId, Notes>,
    /// Stack for UserIds whose rounds have not been played
    next_rounds: Vec<UserId>,
    /// Data for each round
    rounds: Vec<Round>,

    /// Sender to broadcast things
    broadcast_tx: Sender<String>,
    /// Broadcast receiver to send to WebSocket
    broadcast_rx: Receiver<String>,

    senders: HashMap<UserId, Sender<String>>,
}

impl Game {
    /// Game starts.
    fn start(&mut self) {
        assert!(!self.is_started, "Cannot re-start a game");
        self.is_started = true;
        self.active_users = self.senders.keys().cloned().collect();
        self.broadcast_screen(self.screen_compose())
            .context("Broadcast compose screen")
            .unwrap();
    }

    /// User submits a melody.
    fn submit(&mut self, uid: UserId, notes: Notes) {
        if !self.active_users.contains(&uid) {
            warn!(uid=?uid, "Inactive user tried to submit");
            return;
        }
        if self.submissions.contains_key(&uid) {
            warn!(uid=?uid, "User tried to submit twice");
            return;
        }

        self.submissions.insert(uid, notes);

        self.message_screen(uid, self.screen_submitted())
            .context("message submit screen")
            .unwrap();

        if self.active_users.len() == self.submissions.len() {
            info!("All users have submitted");
            let users = self.submissions.keys().cloned();
            self.next_rounds = users.collect();
            self.new_round();
        }
    }

    fn new_round(&mut self) {
        let Some(uid) = self.next_rounds.pop() else {
            error!("No more rounds");
            return;
        };
        self.rounds.push(Round {
            author: uid,
            notes: self
                .submissions
                .get(&uid)
                .context("get users submission")
                .unwrap()
                .clone(),
            guesses: HashMap::new(),
        });

        self.broadcast_screen(self.screen_round())
            .context("broadcast screen round")
            .unwrap();
    }

    fn screen_submitted(&self) -> Markup {
        html! {
            h1 { "Submitted!" }
        }
    }

    fn screen_compose(&self) -> Markup {
        let gid = self.id;
        html! {
            script { ({PreEscaped("document.notes = []; ")})}
            h1 { "Playing Game" }
            p { "Were playing here" }

            canvas
                #canvas
                height=(256) width=(256)
                style="position:relative; background: cyan;"
                {};
            script { (PreEscaped(r#"document.getElementById("canvas").onclick = (e) => {
                const notes = JSON.parse(e.target.dataset.notes ?? "[]");
                notes.push({ time: Date.now(), y: e.layerY / e.target.height});
                e.target.dataset.notes = JSON.stringify(notes);
            }"#))}

            button hx-post=(format!("/game/{gid}/submit"))
                    hx-vals=r#"js:{ "notes": document.getElementById("canvas").dataset.notes }"#
                { "Submit" }
        }
    }

    fn screen_lobby(&self) -> Markup {
        let gid = self.id;
        html! {
            h1 { "Game" }
            p { "Current game id is " (gid)}
            div #messages {};
            button hx-post=(format!("/game/{gid}/start")) { "Start" }
        }
    }

    fn screen_round(&self) -> Markup {
        let i = self.rounds.len();
        let n = self.rounds.len() + self.next_rounds.len();
        let Some(r) = self.rounds.last() else {
            return html! { h1 { "No more rounds" }};
        };

        html! {
            h1 { (format!("Round {i}/{n}"))}
            p { "Author was " (r.author.0)}
        }
    }

    fn broadcast_screen(&self, html: Markup) -> Result<()> {
        self.broadcast_tx
            .send(
                html! {
                    section #content { (html) }
                }
                .into_string(),
            )
            .map(|_| ())
            .context("Failed to send")
    }

    /// Message a single user a screen.
    fn message_screen(&self, user: UserId, html: Markup) -> Result<()> {
        let Some(send) = self.senders.get(&user) else {
            bail!("No such user")
        };
        send.send(
            html! {
                section #content { (html) }
            }
            .into_string(),
        )
        .map(|_| ())
        .context("Failed to send")
    }
}

struct ServerState {
    games: HashMap<u64, Arc<Mutex<Game>>>,
}

impl ServerState {
    fn new_game(&mut self, gid: u64) {
        let (tx, rx) = broadcast::channel(16);
        let g = Game {
            id: gid,
            is_started: false,
            active_users: HashSet::new(),
            submissions: HashMap::new(),
            next_rounds: Vec::new(),
            rounds: Vec::new(),
            broadcast_rx: rx,
            broadcast_tx: tx,
            senders: HashMap::new(),
        };
        self.games.insert(gid, Arc::new(Mutex::new(g)));
    }
}

type Server = Arc<Mutex<ServerState>>;

async fn route_index(State(st): State<Server>) -> Response {
    let game_ids = st.lock().await.games.keys().cloned().collect::<Vec<_>>();

    let game_list = if game_ids.is_empty() {
        html! { "No current games"}
    } else {
        html! {
            h3 { "Games" }
            ul {
                @for id in &game_ids {
                    li { a href=(format!("/game/{id}")) { (id) } }
                }
            }
        }
    };

    let html = html! {
        h1 { "Good game "}
        (game_list)

        button hx-post="/game" { "Create game" }
    };

    html_response(html! {
        (DOCTYPE)
        head {
            meta charset="utf-8";
            title { "Good Game" };
            meta name="viewport" content="width=device-width, initial-scale=1" {};
            script src="https://unpkg.com/htmx.org@2.0.4" {};
            link rel="stylesheet" type="text/css" href="static/style.css";
        }
        body {
            (html)
        }
    })
}

fn html_response(html: PreEscaped<String>) -> Response {
    Response::builder()
        .status(StatusCode::OK)
        .body(Body::from(html.into_string()))
        .expect("Failed to set body")
}

async fn create_game(State(st): State<Server>) -> Response {
    let gid = random::<u64>();

    let _ = {
        let mut s = st.lock().await;
        s.new_game(gid);
    };

    Response::builder()
        .header("hx-redirect", format!("/game/{gid}"))
        .body(Body::empty())
        .expect("failed to build response")
}

async fn start_game(Path(gid): Path<u64>, State(st): State<Server>) -> Response {
    let lock = {
        if let Some(g) = st.lock().await.games.get(&gid) {
            g.clone()
        } else {
            return StatusCode::NOT_FOUND.into_response();
        }
    };

    lock.lock().await.start();

    StatusCode::OK.into_response()
}

async fn get_game(
    Path(gid): Path<u64>,
    Extension(uid): Extension<UserId>,
    State(st): State<Server>,
) -> Response {
    let game = {
        if let Some(g) = st.lock().await.games.get(&gid) {
            g.clone()
        } else {
            return (StatusCode::NOT_FOUND).into_response();
        }
    };

    let html = {
        let g = game.lock().await;
        if !g.is_started {
            g.screen_lobby()
        } else if g.rounds.len() == 0 {
            if g.submissions.contains_key(&uid) {
                g.screen_submitted()
            } else {
                g.screen_compose()
            }
        } else {
            // TODO
            warn!("Wrong screen");
            g.screen_lobby()
        }
    };

    html_response(html! {
        (DOCTYPE)
        head {
            meta charset="utf-8";
            title { "Good Game" };
            meta name="viewport" content="width=device-width, initial-scale=1" {};
            script src="https://unpkg.com/htmx.org@2.0.4" {};
            script src="https://unpkg.com/htmx-ext-ws@2.0.1/ws.js" {};

            link rel="stylesheet" type="text/css" href="/static/style.css";
        }
        body hx-ext="ws" ws-connect=(format!("/game/{gid}/ws")) {
            footer { }
            section #content {
                (html)
            }
            footer { span { "You are " (uid.0) } }
        }
    })
}

async fn submit_game(
    Path(gid): Path<u64>,
    State(st): State<Server>,
    Extension(uid): Extension<UserId>,
    Form(form): Form<NotesForm>,
) -> Response {
    let glock = {
        if let Some(g) = st.lock().await.games.get(&gid) {
            g.clone()
        } else {
            return (StatusCode::NOT_FOUND).into_response();
        }
    };

    let Ok(notes) = serde_json::from_str(&form.notes) else {
        warn!(notes = form.notes);
        return (StatusCode::UNPROCESSABLE_ENTITY).into_response();
    };

    glock.lock().await.submit(uid, Notes { notes });
    StatusCode::OK.into_response()
}

async fn game_ws(
    ws: WebSocketUpgrade,
    Path(gid): Path<u64>,
    Extension(uid): Extension<UserId>,
    State(st): State<Server>,
) -> Response {
    let game = {
        let s = st.lock().await;
        if let Some(g) = s.games.get(&gid) {
            g.clone()
        } else {
            return StatusCode::NOT_FOUND.into_response();
        }
    };

    ws.on_upgrade(move |socket| handle_socket(socket, uid, game))
        .into_response()
}

async fn handle_socket(mut socket: WebSocket, uid: UserId, game: Arc<Mutex<Game>>) {
    if socket
        .send(Message::Ping(bytes::Bytes::from("wat")))
        .await
        .is_ok()
    {
        trace!("Pinged ws");
    } else {
        println!("Could not send ping!");
        return;
    }
    let mut single_rx = {
        let mut g = game.lock().await;
        // g.broadcast_tx
        //     .send(
        //         html! {
        //             div #messages hx-swap-oob="beforeend" { p { "Someone joined" } }
        //         }
        //         .into_string(),
        //     )
        //     .unwrap();
        let (tx, rx) = broadcast::channel(16);
        g.senders.insert(uid, tx);
        rx
    };

    let mut broadcast_rx = { game.lock().await.broadcast_rx.resubscribe() };

    loop {
        tokio::select! {
            res = single_rx.recv() => {
                if let Ok(msg) = res {
                    let res = socket.send(msg.into()).await;
                    if res.is_err() {
                        warn!(res=?res, "Error from socket.send");
                        break;
                    }

                } else {
                    warn!(res=?res, "Error from single_rx");
                    break;
                }
            },
            res = broadcast_rx.recv() => {
                if let Ok(msg) = res {
                    let res = socket.send(msg.into()).await;
                    if res.is_err() {
                        warn!(res=?res, "Error from socket.send");
                        break;
                    }

                } else {
                    warn!(res=?res, "Error from broadcast_rx");
                    break;
                }
            },
        }
    }
}

#[derive(Hash, Eq, PartialEq, Copy, Clone, Debug)]
struct UserId(u64);

async fn identity_middleware(jar: CookieJar, mut req: Request, next: Next) -> Response {
    const UID: &'static str = "uid";

    let opt_uid = jar.get(UID);
    let uid = opt_uid
        .and_then(|c| c.value().parse::<u64>().ok())
        .unwrap_or_else(|| random::<u64>());
    let uid = UserId(uid);

    req.extensions_mut().get_or_insert::<UserId>(uid);

    let mut res = next.run(req).await;

    if opt_uid.is_none() {
        let cookie = cookie::Cookie::build(("uid", uid.0.to_string()))
            .same_site(cookie::SameSite::Strict)
            .path("/")
            .http_only(true)
            .secure(true)
            .build();
        res.headers_mut()
            .append("Set-Cookie", cookie.encoded().to_string().parse().unwrap());
    }

    res
}

#[tokio::main]
async fn main() -> Result<()> {
    let subscriber = FmtSubscriber::builder()
        .with_max_level(Level::TRACE)
        .finish();
    tracing::subscriber::set_global_default(subscriber)
        .expect("set global default subscriber failed");

    let mut server_state = ServerState {
        games: HashMap::new(),
    };
    server_state.new_game(123);

    let st = Arc::new(Mutex::new(server_state));

    let app = Router::new()
        .route("/", get(route_index))
        .route("/game", post(create_game))
        .route("/game/{gid}", get(get_game))
        .route("/game/{gid}/start", post(start_game))
        .route("/game/{gid}/submit", post(submit_game))
        .route("/game/{gid}/ws", get(game_ws))
        .nest_service("/static", ServeDir::new("static"))
        .layer(CatchPanicLayer::custom(handle_panic))
        .layer(
            TraceLayer::new_for_http()
                .make_span_with(DefaultMakeSpan::new().level(Level::INFO))
                .on_response(DefaultOnResponse::new().level(Level::INFO)),
        )
        .layer(middleware::from_fn(identity_middleware))
        .with_state(st.clone());

    let addr = "0.0.0.0:4800";
    info!("Listening on {addr}");
    let listener = tokio::net::TcpListener::bind(addr).await.unwrap();
    axum::serve(
        listener,
        app.into_make_service_with_connect_info::<SocketAddr>(),
    )
    .await
    .context("serve")
}